1. Field of the Invention
The present invention relates to optical products such as spectacle lenses and spectacle plastic lenses.
2. Description of Related Art
In plastic optical products, an optical multilayer film as an antireflection film is formed on the surface in order to reduce light reflection from the surface. Such an optical multilayer film is formed by alternately stacking several low refractive index and high refractive index layers, and an antireflection film having W-shaped spectral distribution of reflectance with a local maximum point at around 520 nm (nanometers) is commonly used in view of processing stability and appearance. Thus, upon incidence of light on the optical product having the optical multilayer film, a light green reflected image is seen when the optical product is viewed from the light incidence side (this phenomenon can also be seen in spectacle plastic lenses).
An optical product that allows a reflected image having such a light green reflected color to be more faint and inconspicuous is suggested by the inventor of the present invention in Japanese Laid-Open Patent Publication No. 2012-042830. In the optical product described in Japanese Laid-Open Patent Publication No. 2012-042830, reflected light has a color in a colorless and transparent range (0.27≦x≦0.30 and 0.30≦y≦0.36) on the chromaticity diagram (x,y,Y) of the CIE color system, and reflectance is 1% (percent) or less in a visible region, that is, the reflectance is very low. In a case where a total of seven layers are stacked such that a low refractive index layer and a high refractive index layer alternate, a total physical film thickness of the fourth layer or the fourth and fifth layers is preferably set so as to be in a specific range, whereby reflected light has a color in the aforementioned range on the chromaticity diagram, and the reflectance is made very low.